(a) Field of the Invention
This invention relates to cationic azo dyestuffs. More particularly, the present invention relates to novel water-soluble quaternary ammonium azo dyestuffs useful in the dyeing art, particularly for coloring natural fibers, synthetic fiber-forming material and cellulosic materials such as threads, sheets, fibers, filaments, textile fabrics and the like, as well as in the manufacture of paper, varnishes, inks, coatings and plastics.
(b) Description of the Prior Art
A number of quaternary ammonium azo compounds of widely diverse structural types are known to be useful as dyestuffs for coloring synthetic fibers and cellulosic materials in various shades of yellows, reds and oranges. For example, U.S. Pat. No. 2,821,526, patented Jan. 28, 1958 teaches monoazo dyes bearing a quaternized group of the type ##STR3## useful for dyeing acrylic fiber or acrylic fiber in mixture with cellulosic fiber; U.S. Pat. No. 2,945,849, patented July 19, 1960 teaches in particular unsymmetrical disazo compounds containing a quaternary ammonium group of the type -N(C.sub.2 H.sub.5)CH.sub.2 CH.sub.2 N.sup..sym. (CH.sub.3).sub.3 which are useful for dyeing and printing polymers of acrylonitrile; U.S. Pat. No. 3,524,842, patented Aug. 18, 1970 teaches water-soluble cationic phenylazonaphthol dyestuffs bearing a simple quaternary ammonium moiety which are useful for dyeing tanned cotton; and U.S. Pat. No. 3,729,459, patented Apr. 24, 1973 discloses quaternized monoazo dyestuffs bearing a quaternary ammonium moiety of the type --N(C.sub.2 H.sub.5)CH.sub.2 CH.sub.2 N.sup..sym. (CH.sub.3).sub.2 C.sub.6 H.sub.5. However, heretofore known water-soluble quaternary ammonium azo and disazo dyestuffs have suffered from a number of deficiencies when employed as dyes for coloring cellulose in the form of bleached pulp of the type used for the manufacture of household paper goods such as paper napkins, paper toweling, facial tissues and so forth. Thus, they have been found to undesirably bleed out of paper products colored with them when the article is brought into contact with water, milk, soapy solutions or other common household solutions. They have also been found to have relatively poor substantivity to bleached pulp and have suffered from a low rate and degree of exhaust from dyeing solutions containing them. There is thus a need for water-soluble dyestuffs for coloring bleached pulp which have high bleed resistance, good substantivity and a high rate and a high degree of exhaust from aqueous dyeing solutions in which they are utilized. It has surprisingly been found that the quaternary ammonium azo compounds of the instant invention possess these desired properties and consequently are particularly well adapted as dyestuffs for bleached pulp.